114 DR. O. STAPF ON THE FLORA OF MOUNT KINABALU. 
600 or 700 feet would be sufficient to join Borneo to the mainland, to Sumatra and 
Java, and to the Philippines, and it would bring Celebes in reach within a few miles. 
Celebes itself would extend far enough to include Buru, and thus be brought very close 
to Ceram and New Guinea. A shifting of 1600 to 1700 feet, however, would complete 
the union of Borneo with Austro-Malaya, including New Guinea, and with Australia (see 
Berghaus, ‘ Physik. Atlas,’ no. 25). Yet I doubt whether such a change by itself would 
be sufficient to cause a considerable exchange of the highland floras concerned. It would 
raise some of the lower spurs and ranges, with which the highland of Kinabalu is at 
present connected at low levels, to such altitudes that they might exchange a part of 
their present flora with a flora more like the one living now on Kinabalu in similar 
altitudes. Something of this kind would happen in Sumatra or in any other part of the 
united land, and, no doubt, the various highlands would be brought closer together. A 
simultaneous depression of the lines of vegetation such as might have occurred, for 
instance, during a period of extreme glaciation, without seriously impairing the tropical 
vegetation of the lowland, would have favoured the exchange still more. There would, 
however, still have been wide lowlands having a tropical climate and a tropical] flora 
where there is now sea, and these lowlands would have been almost as strong a barrier 
for the highland flora as the sea is now. But such a state is hardly conceivable without 
some simultaneous change in the surface of the land. The denudation which takes place 
in the highland before our eyes is enormous. Its configuration and that of the 
surrounding land show clearly enough that it has been going on at this rate for a long 
time. Then the highland must once have been far more extensive, if not also higher. It 
most probably shared this denudation with the remainder of the Bornean highlands, the 
detritus of which is deposited in the vast Tertiary strata which cover one half or more of 
Borneo. Other highlands beside this have very likely existed in the former Malayan 
continent, and, in connection with them, highlands which made the invasion of a northern 
and of a southern element of more or less temperate character possible. In fact, the 
assumption of such highlands seems to me the conditio sine quá non for under- 
standing the history of the flora of Kinabalu and of the highland flora of Malaya 
generally. 
A more exact determination of the lines over which, and of the time when, the 
exchange took place is hardly possible at present. It could be undertaken only on the 
basis of a comparative study of the entire highland flora of the Malay Archipelago and 
of a more complete knowledge of the geology of the region. I restrict myself, therefore, 
to a few general remarks referring to this question. 
.. Beccari (* Malesia,’ i. pp. 219, 220) was of opinion that the Boreal alpine element on 
the high volcanoes of Java must have immigrated at a very recent date, as the volcanoes 
- themselves are so very recent. Their habitats on these volcanoes are, of course, as recent 
. as or more recent than the volcanoes. But this does not necessarily imply that they did 
not already exist in this part of Malaya before the volcanoes were thrown up. We know 
that the Javan volcanoes rest upon Tertiary strata, and traces of the old Schistose Forma- 
e tion phieb occupies so much space in Sumatra were discovered only some ten years ago. 
The r toecni volcanoes of Sumatra, on the other hand, rest upon this Schistose Formation, 
